'Pyrographite', a synonym for pyrolytic graphite, was introduced as a trademark and should not be used as a term. Hot working of pyrolytic
graphite (by heat treatment under compressive stress at temperatures above
) results in
highly oriented pyrolytic graphite (HOPG).

Source:

PAC, 1995, 67, 473
(Recommended terminology for the description of carbon as a solid (IUPAC Recommendations
1995))
on page 502